h4 visa expiry date when came back to india before my visa expiry date?

i am with h4 visa… its valid date upto december 2014… i came back to india in august 30th 2013. how many months i can stay in india. what is expiry date for my dependent visa after coming to india… i want to go back to usa in august 2014… if i stay more than 6 months in india my visa will expire or not?